// The following HTTP request code borrowed from JavaScript: The Definitive Guide, 5th Edition, Example 20-1, from O'Reilly Publishing.
var HTTP = {};
// --- Start of borrowed code ---
// This is a list of XMLHttpRequest-creation factory functions to try
HTTP._factories = [
    function() { return new XMLHttpRequest(); },
    function() { return new ActiveXObject("Msxml2.XMLHTTP"); },
    function() { return new ActiveXObject("Microsoft.XMLHTTP"); }
];

// When we find a factory that works, store it here.
HTTP._factory = null;

// Create and return a new XMLHttpRequest object.
//
// The first time we're called, try the list of factory functions until
// we find one that returns a non-null value and does not throw an
// exception. Once we find a working factory, remember it for later use.
//
HTTP.newRequest = function() {
    if (HTTP._factory != null) return HTTP._factory();

    for(var i = 0; i < HTTP._factories.length; i++) {
        try {
            var factory = HTTP._factories[i];
            var request = factory();
            if (request != null) {
                HTTP._factory = factory;
                return request;
            }
        }
        catch(e) {
            continue;
        }
    }
    // If we get here, none of the factory candidates succeeded,
    // so throw an exception now and for all future calls.
    HTTP._factory = function() {
        throw new Error("XMLHttpRequest not supported");
    }
    HTTP._factory(); // Throw an error
}
// --- End of borrowed code ---

function toggleDiv(name)
{
	var e = document.getElementById(name);
	try {
		var s = e.style;
		s.visibility = ((s.visibility == "visible") ? "hidden" : "visible");
	} catch (error) { 
		//alert(name + " " + error);
	}
}

function toggleCover()
{
	toggleDiv("cover");
}

function updateOverheards(newHTML)
{
	var list = document.getElementById("overheardlist");
	list.innerHTML = newHTML + list.innerHTML;
}

function submitOverheard()
{
	// get form data

	var overheard = document.getElementById("ovrhrd").value; 
	var overheardby = document.getElementById("ovrhrdby").value;

	// create request object
	var request = new HTTP.newRequest();

	request.onreadystatechange = function() {
		if(request.readyState == 4 && request.status == 200 ) {
			updateOverheards(request.responseText);
		}
	};

	request.open("POST", "postOverheard.php");
	
	request.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");

	var filter = /%20/g;

	var data = "Quote=" + encodeURIComponent(overheard).replace(filter,"+");
	data += "&Postby=" + encodeURIComponent(overheardby).replace(filter,"+");
	request.send(data);
}

function centerElement(name, w, h)
{
	e = document.getElementById(name);
	var s = e.style;
	try
	{
		s.left = ((parseInt(window.innerWidth) - w) / 2) + "px";
		s.top = ((parseInt(window.innerHeight) - h) / 2) + "px";
	}
	catch (error)
	{
		s.left = ((parseInt(document.documentElement.clientWidth) - w) / 2) + "px";
		s.top = ((parseInt(document.documentElement.clientHeight) - h) / 2) + "px";
	}
}

function resizeCenteredElements()
{
	centerElement("overheardform", 400, 200);
}